Wire rope has long been manufactured to meet very demanding conditions--in its employment in cranes, hoists, drag lines, elevators, ski lifts, various marine environments and mining machinery, it is commonly exposed to the elements and frequently flexed, abraded and tensed under extreme loads. While wire rope intended for such uses has always been made as rugged as economics will permit, its expense is such that a constant search is underway for ways to increase the hours-in-use before it must be replaced.
Various approaches have been employed in the past to reduce wear and increase the life of wire rope.
For example, it is not new to orient the outer strands of the rope in the same lay (i.e. to make a complete 360.degree. helical turn in the same linear measure of rope) with the inner strands so that contact between wires of the inner and outer strands is linear rather than at particular points See U.S. Pat. 3,306,022. The basic idea of internally lubricating wire rope has also been disclosed--see U.S. Pat. Nos. 3,705,489; 2,485,019; 3,824,777 and the prior art recited in U.S. Pat. No. 4,344,278. Stress-relieving has also been practiced at an intermediate stage of wire rope making: U.S. Pat. No. 3,240,570. Likewise it is known (see U.S. Pat. No. 3,718,442) to employ steel of a certain metallurgy, particularly containing a small amount of vanadium and an optional amount of molybdenum in order to improve ductility and other characteristics of the strands. Mixtures of thermoplastic materials and lubricants are disclosed to be useful in the interiors of certain wire ropes--see U.S. Pat. Nos. 4,120,145; 4,123,894 and 2,372,142. For other disclosures generally in the art of making wire rope, see U.S. Pat. Nos. 3,075,344; 3,259,487; 3,293,837; 3,271,944; 3,668,020; 3,374,619 and U.S. Pat. No. Re. 29,537. None of these combines the features of my invention.